If theyre covering a steep slope roof with a tar-like substance, then caveat emptor (or something like that). They are covering up problems, and roofing on a Victorian is big bucks. Most are three stories up, very steep, and very cut-up. Very labor intensive.

You might consider paying a professionally licensed and insured roofing contractor to perform an inspection and possibly provide a written estimate or proposal for work.

Sounds like you are looking at a house in the Baltimore area. Seriously, I’ve seen a lot of Baltimore roofers use hot asphalt to coat leak areas in shingle roofs, and it is not something that I would ever recommend.

What type of roof is on the Victorian house you are looking at? Does it have shingles, shake, slate, etc? Aaron makes a good point about getting an estimate for repairs/replacement, and then using that price as a bargaining chip in negotiating a sale price on the house. I would also recommend that you go into the attic and visually inspect the structure for water damage, etc.